Recently preheating of oxygen-fuel with waste energy from flue gas for oxygen-fuel combustion has been demonstrated for glass industries as a promising solution to reduce natural gas consumption, thereby decreasing CO2 emissions. The technology demonstrated combustion efficiency increases about 9-10%, which means 9-10% of savings of oxygen and natural gas when oxygen and natural gas are preheated to 500° C. and 450° C., respectively. Although the technology development is relatively successful, there is room for improvement in waste energy recovery.
Operating a steam methane reformer (SMR) using waste energy from a glass or steel reheating furnace has been discussed for a long time and the technology of fuel conversion using waste energy coupled with a SMR is commonly called Thermo-Chemical Recuperation (TCR). However, a challenge in combining an oxygen-fuel pre-heated furnace with a typical SMR is the temperature of available hot air generated from wasted flue gas is only about 680-700° C. at maximum, which is well below the temperature required to properly run a SMR that requires at least 800° C. The temperature of the waste flue gas from a glass furnace is generally about 1000° C. or above. However, the waste flue gas contains sulfuric acid which causes sulphate condensation in a low temperature portion of a flue gas channel. The waste flue gas also contains particulates that are harmful to the SMR. Thus, although the waste flue gas has thermal energy to run a SMR, if directly applying the waste flue gas from a glass furnace to operate the SMR, there will be problems of particulates presented in the entire flue gas channel and sulfuric acid and sulphate condensation in a low temperature portion of a flue gas channel.
Attempts to recycle waste energy applying TCR technology have been done. Chen et al. (EP0464603 B1) disclose the use of commercially pure oxygen in a glassmaking furnace with recovery of heat from the offgas by at least partially reforming furnace fuel, which offgas is predominately carbon dioxide due to the oxygen purity and which carbon dioxide can be recovered for recycle and for export as product.
Kapoor et al. (EP0643013 A1) disclose a hot exhaust gases (from oxygen-based hydrocarbon-fire) furnace made up predominantly of steam and carbon dioxide are used for reforming in a reformer a hydrocarbonaceous substance in the presence or absence of oxygen to produce carbon monoxide and hydrogen. Additional hydrogen can be produced by subjecting the carbon monoxide produced in the reaction to the water gas shift reaction.
Basu et al. (EP1071867 B1) disclose a portion of flue gas from burning a reformed fuel is directed to a gas turbine to produce power and the remaining flue gas mixed with hydrocarbon to produce reformed fuel which is burnt in a combustor.
Chudnovsky et al. (US2009/0011290 A1) disclose a two-stage heat exchange vessel. The first stage performs reforming using heat from the exhaust and the second recuperator is used to preheat oxidant for combustion.
Kweon et al. (U.S. Pat. No. 7,210,467) disclose an apparatus including a reciprocating internal combustion engine and a TCR in which a fuel is reformed. The TCR is heated by exhaust gases from the reciprocating internal combustion engine and steam for the reforming process is produced by passing feed water through an engine lubricating oil heat exchanger, an engine cooling system heat recovery system and an exhaust gas heat recovery system arranged in series.
These attempts to recover the waste energy by reforming or partially reforming the fuel gas have not shown any applications to systems that have no enough available energy to run a reforming process to fuel, for example, oxygen-fuel pre-heated combustion systems.
Thus, there remains a need to provide a solution for use of the waste energy and/or use of a hot air stream generated from the waste energy (e.g., flue gas) in the oxygen and fuel preheated combustion systems.